ELECTRONIC DEVICES - LEARN ELECTRONICS

CAPACITORS

Our discussion on resistors is certainly not complete and I would like to touch on it again later when I expose you to SMD's (surface mounted devices). However I promised to discuss capacitors but I'd like to keep it short as I would firstly like to cover electronics in general before we continue with electronic components.

Capacitors or caps as they are more commonly known by the initiated, comes in various shapes and sizes, forms and ratings, meaning it can be shaped like anything from a matchstick's head to that of a bullet's casing. They can be as small as a pin's head to as large as a cake tin and shaped like that as well. They can be rated to withstand as little as 1.5Volts across their terminals to several hundred volts and when the rated voltage is exceeded or the polarity reversed, they may explode. Yes, you read right, capacitors do explode and they make a really loud bang and the smell that accompanies it takes some getting used to. However, some capacitors are polarity conscious, then there some that are not. Reversing the polarity on a capacitor willfully is not a good idea, so always make certain you insert a cap into a PCB correctly. Capacitance which is the property of caps is measured in Farads. A one farad capacitor could be as large as a car coil or a litre bottle but all caps are tiny compared to this, so we use micro farads, (millionths of farads) instead. The symbol for micro farads is μF. (the character that looks like a U is the greek character mu) Caps are produced from various materials like cardboard and foil paper placed in aluminum canisters along with electrolyte, some are ceramic encapsulated. Other are just two metal electrodes separated by glass and air. You will not be required to make caps, but rather buy them from the thousands of electronic component dealers world wide.

Caps have the ability to pass AC (alternating currents) and block DC (direct current) and are used extensively in power supplies where the charge and discharge rates are key to smooth out any interference from the input power. Essentially, caps can be describes as to wires (called electrodes) physically isolated, with a substance in between them, which is capable of storing the potential difference developed between the two electrodes. Restated caps can hold a charge if subjected to it, sometimes for a few days but it will decay over time. However, should you touch both electrodes of a cap that is charged by mains voltage, with your bare hands, it can really get your attention, it will give you a really mean electric shock. So now that I scared away the timid, let me go to the electronics discussion, but will return to caps later.

A TV aerial made of aluminum may not seem like an electronic device, but it does contain a tiny PCB (printed circuit board) which supports two or three ceramic caps along with a coil or two to which the coaxial cable gets to be attached. This aerial's shape and size has been mathematically calculated based on harmonics of the signal its suppose to receive, and along with the caps, form a tuned circuit targeted for a specific frequency range, Hence you get VHF aerials, UHF aerials, whip aerials, dipole aerials etc etc...

A heatsink has no electrical properties and its normally just a piece of aluminum attached to or to which some electronic component is attached in order to keep it cool. A microprocessor's heatsink for example would even have a fan fitted onto of the aluminium to stop the microprocessor from going into thermal runaway. Aluminum has a good heat dissipation factor hence it is predominantly used in electronics even though at times copper is also used as heatsinks.

A transformer is normally two coils of wire isolated from one another but coexisting in close proximity on the same core which is often made of ferrite but also mild steel plates. These plates are composed of E shaped plates and I shaped plates oppositely interleaved to created numerous figure 8s, then packed on top of one another. The two holes in the figure 8 is where these coils of wire live. The core of the transformer is were eddy currents rise and fall to cause magnetism which roughly describes transformer action.

A speaker is like a transformer except that the current driving its coil is powered by an amplifier rather than mains electricity, which creates magnetism to drive its cone which intern displaces air. The moving air interacts with our eardrums which we interpret as sound.

A microphone is the inverse of the speaker and roughly uses the same technology whereby our voices moves its diaphragm, which moves across a magnet to produce a current in its coil destined as input to an amplifier. Speakers and microphones are essentially called transducers but we will have to return to that topic at a later date.

A relay is essentially a remote switch which can have numerous contacts to switch heavier loads than what the relay switch can handle. Relays come in various sizes and various current ratings. Relays in essence are mechanical contacts controlled by an electromagnetic field, created by a coil which moves a mechanical lever or plunger which is responsible for the electrical switching.

I will continue with this discussion next blog.  If you find this blog interesting please recommend it to others by clicking on the g+1 below.